Currently, instruments used in a wide range of applications such as manufacturing or research and development have achieved a high level of sensitivity with respect to the job they perform. Many of these same instruments also require a correspondingly accurate alignment to perform or interact with other similarly sensitive instruments. Unfortunately, many of the environments which these instruments are required to operate in are not conducive to the accurate performance of the instruments. For instance, floors or tables upon which the instruments rest are not level, or nearby motor vehicle traffic causes vibration that introduces misalignment.
An optical tracking system disclosed in U.S. Pat. No. 3,757,125 to Okada et al. uses the phase of light reflected from an object to determine the objects position relative to a selected position of the object. The apparatus taught by Okada et al. is typical of most known tracking systems in that the position of the object is determined by directly tracking it. From the determined position a feed back loop is utilized to stabilize the object. One significant problem with such a tracking system is the range the system is able to track an object. If the object being tracked moves essentially a small distance, then the object becomes out of range and tracking ends.
An apparatus that has been used to determine the position of a light beam with respect to tracking for misalignment purposes is the four-quadrant photodetector. For example, U.S. Pat. No. 3,579,140 to Anderson et al. discloses a four-quadrant photodetector for use in aligning a continuous wave laser.
Scanning systems have also used orthogonal deflection to control a light beam with respect to two dimensions. U.S. Pat. No. 4,314,154 to Minoura et al. discloses a two-dimensional scanning device having compensation for scanned image strain.
None of the aforementioned devices expands the range an object can be followed, nor do they take advantage of indirect tracking of an object of interest.
The present invention is a tracking system that provides a much greater tracking range than heretofore known. The present invention, instead of tracking the object directly, utilizes a light beam associated with the object. The light beam is deflected through an orthogonal deflection system, which controls the position of the light beam with respect to two dimensions, onto a detector such as a four-quadrant photodetector that determines the position of the light beam. By knowing the position of the light beam on the detector, the position of the object from which the light beam eminates is determined. The use of orthogonal deflection, and the tracking indirectly of the object by way of the detector, allows for a much greater tracking range of movement of the object. The position of the object is then able to be controlled with some form of a feedback loop.